External sewer networks. External sewerage: device according to SNiP How an external sewerage network is installed

July 18, 2016
Specialization: Capital construction work (laying a foundation, erecting walls, constructing a roof, etc.). Internal construction work (laying internal communications, rough and fine finishing). Hobbies: mobile communications, high technology, computer equipment, programming.

It's no secret that I'm going to build a dacha house for my son in the near future. And now I’m designing engineering communications for the future structure. In particular, external sewerage is on the agenda.

The design of this system, although it seems quite simple, especially in comparison with branched pipelines laid inside the house, has many nuances. Violation of certain requirements can lead not only to system inoperability, but also to dangerous consequences for others. And then the estimate should be smaller, because after all, I’m going to spend my own money, not government money.

In general, we had to tinker a lot. But as a result, I can provide you with detailed instructions about how to properly design and install this system yourself. Read carefully.

Building code requirements

First, let’s look at what external sewerage is according to SNiP. After all, you don’t want your future home to not comply with the established standards and not be accepted for operation by the relevant services. So I don’t want something like this for my offspring’s dacha, so I’ll dwell on covering the issue raised in more detail.

Elements of external sewerage

The external part of the wastewater removal system is necessary for transporting sewage to places of its processing and cleaning it from various contaminants.

It consists of several elements:

Pipelines of various sections and lengths. They are made from different materials and serve to deliver wastewater from the drain pipe of the internal pipelines of the house to treatment facilities (centralized or autonomous).
Wells. They are an essential part of the sewer system and are necessary to perform certain actions.

In my practice I have encountered the following types of wells:

to inspect communications (they are used to clean clogged pipes);
for arranging pipeline turns;
for laying pipes with height differences;
drainage

Collectors. They are unique pipelines of huge diameter that serve to accumulate and transport sewage water in centralized wastewater disposal systems.
Treatment plants. They are central (on locality or part of it) and local (used to clean sewers in a private house). In the latter case, the treatment facility can be replaced by a storage tank, which is periodically emptied using sewage disposal equipment.

Swap stations. An intermediate link in the treatment system that accumulates wastewater and gradually delivers it to the treatment facility. Such units are used in centralized networks or privately if a station is installed on the site biological treatment with aerobic bacteria.

Above I listed the main elements of the system. But to install an external sewer network, you will need many more materials and tools, which I will talk about below.

polymer - polypropylene, polyethylene, polyvinyl chloride;
steel and cast iron pipes are an outdated option, since the price of such parts is high, and the performance properties leave much to be desired;
asbestos-cement and reinforced concrete channels - used only in centralized sewers; I have not seen them in private houses.

I also heard that there are pipes made of ceramics and glass, but I haven’t seen them in practice, so I can’t tell you anything specific. But this is a very exotic material, which is certainly not useful in private construction.

General installation rules

Regardless of size, performance and other parameters, when creating local external sewage systems, it is necessary to adhere to certain sanitary and construction rules.

The regulatory documents contain a lot of information, but for an ordinary master doing sewerage in his own country house, it is enough to take into account the following factors:

groundwater level at the site;
soil properties;
the climate of the area in which construction is taking place;
the average volume of sewage that is planned to be disposed of per day;
the distance from the house to the central sewer collector or autonomous septic tank.

One of the main requirements that must be strictly observed (otherwise your outdoor system the sewer system simply will not work) - this is the slope of the pipelines. The specific value depends on the diameter of the parts. To make it more clear to you, I have compiled a small table.

Before starting work on creating an external drainage system, I advise you to order survey work to study the soil, lay out the pipeline route, calculate the necessary parts and the cost of the work.
If you don’t want to do all this, at least ask for advice from those neighbors who have already completed work on installing utility systems.

Requirements for external piping

Before choosing a specific type of pipe and starting work, I want to list the most important requirements that apply to external sewerage systems (they are enshrined in SNiP number 2.04.03-85):

The outer part of the sewer system must be constructed from materials that have the longest service life and are not subject to corrosion. After all, it will be operated in very aggressive conditions.

When laying pipelines, it is necessary to take into account the nature of the soil in order to avoid soil shifts after filling the parts. Otherwise, a leak will occur, which can become a source of groundwater contamination.
In the design of an external drainage system, it is necessary to provide for the presence of mandatory elements: inspection holes, valves, pipes, pumps, and so on. Believe me, all the rules were created for a reason, and you will greatly regret it in the future if you cannot clean the pipes due to lack of audit.
It is imperative to install inspection wells and hatches in places where pipes turn, where individual pipeline threads intersect, and where revisions occur. Otherwise, in the event of an accident, excavation work will have to be carried out. Wells must have safety elements (hatches, fences, ladders, etc.).

Construction of external sewerage

So, let's look at how external sewage is made. I divided all the arrangement work into several parts. But remember that specific instructions depend on whether you are connecting the pipelines in the house to a central sewer or building your own treatment plant.

But first things first.

Pit preparation

Installation of external sewerage begins with preparing a pit, or more precisely, a trench for laying pipes. You can dig it simply with a shovel (if the length is not very large) or order an excavator.

The depth of the hole directly depends on the depth of soil freezing in the area where you live. External sewerage pipes must be laid 50 cm below this mark. You can find the necessary information in special tables.

The approximate depth of soil freezing in different regions of Russia is:

in the northern regions of the Russian Federation - from 3 to 3.5 meters;
in the middle zone of our country - from 2.5 to 3 meters;
V southern regions on the Black Sea coast - from 1.2 to 2 meters.

The values given are approximate. This is why I advise you to conduct a soil study in the area where your house is built.

Most often, pipes with a diameter of 110 mm are used for installation of the external part of the sewer system. For them, I recommend digging a trench 60 cm wide (to make installation convenient). Depth – freezing level + 50 cm according to SNiP + 10 cm for the installation of a shock-absorbing cushion.

In addition, when digging a ditch for laying sewer pipes, I pay attention to several other features:

I always carefully level the bottom of the recess and make a slope, which I already mentioned above. It is necessary to ensure free flow of water towards the collector or its own treatment plant.

Once I have leveled the bottom, I carefully compact the soil below to avoid shifts. Then I pour a 10 cm thick sand cushion on top, which I also compact very carefully.
The fact is that the pipes are assembled using sockets, so soil shifts can lead to depressurization of the system. But I, for example, don’t want to dig up three meters of earth again to find a leak. Moreover, you will have to dig along the entire length.
In those places where the pipe enters the collector or, it is necessary to make more wide platform(at least two meters), the bottom of which should also be thoroughly compacted and covered with sand.

Sockets and shaped parts have several big sizes than the pipe itself. Therefore, in the places where they will be installed, I always make pits so that the central axis of the pipe is always at the same level (naturally, with a slope from the house).

Pipe laying

Having finished with the hole, you can safely move on to laying the pipes. However, before that I want to say a few words about choosing the right material.

I will not mention citywide networks now, since large companies are involved in their construction. And for a private house or cottage, in my practice I used polymer pipes:

polyethylene;
polypropylene;
polyvinyl chloride.

If pipes will be laid at very great depths or this section of soil will be subject to frequent and significant dynamic loads, it is better to buy high-strength corrugated pipes made of polyethylene or propylene. They are joined together using shaped parts.

In all other cases, I use polyvinyl chloride pipes with sockets. If you have designed an internal sewer system, then you know what I mean. You just need to take not the gray parts that are familiar to you, but those varieties that are painted orange.

They are quite durable, have a smooth internal surface and are perfect for constructing external engineering wastewater disposal systems. The maximum that these pipes can be buried is 3 meters, which is quite enough for most cases.

I lay the pipes according to the following scheme:

First, I lay out all the pipes at the bottom of the trench without trimming. I put revisions, tees, crosses and other necessary shaped parts in the right places.
Then I begin the assembly, which I start from the inlet pipe of the collector or local septic tank. To do this, I take the parts cut to the required size and clean them of dust and dirt.

If you are cutting pipes with a saw rather than a pipe cutter, the end of the part must be cleared of burrs and a small chamfer removed, otherwise the rubber O-ring may be damaged. I also recommend making sure that the cut is positioned exactly at an angle of 90 degrees relative to the surface of the pipe.

After cleaning, I insert the smooth part of one pipe into the socket of the other until it stops. To provide an extra seal and extend the life of the seal, I always coat it with silicone sealant.
I proceed in the same way with the remaining parts along the entire length of the pipeline.

I would like to give one free piece of advice. If the external sewer piping design involves sharp turns, do not use 90-degree angles. It is better to install two at an angle of 45 degrees. And be sure to install a well with an inspection in this place.

This will save you from trouble and allow you to quickly clean a difficult area if it happens.

In this way, you need to collect all the pipes into one system and test them for leaks. To do this, you need to pour a bucket of water into the pipe of the internal sewerage system and wait until it enters the central collector or your own septic tank (more on that a little later).

Insulation

Very often, when constructing an external sewer system, I resorted to additional insulation of the plastic pipes used. Strictly speaking, if you have dug a trench of sufficient depth (below the soil freezing level), there is no need for insulation, but, as they say, it is better to be safe.

The following can be used as thermal insulation material:

glass wool or basalt fiber;
polystyrene;
polyurethane foam;
heat-insulating.

I advise you not to rack your brains over the choice of material and buy insulating shells made of extruded polystyrene. It has a fairly low thermal conductivity coefficient, high water-repellent properties, long service life and increased strength.

Among other things, to install it on pipes you do not need to resort to any tricks. It is enough to mount the halves of the shell on the pipe and snap them onto special locks, wrapping them with adhesive tape on top to be sure.

This is much easier than wrapping pipes with mineral wool, then securing it, then wrapping roofing felt on top, and so on.

backfilling

The last stage of constructing an external sewer pipeline is backfilling the trench. I do not advise treating this stage with disdain, since this is where beginners often make mistakes. a large number of errors.

For backfilling, you can use the soil that was removed from the trench. First you need to make sure that there are no clods of earth, stones and other objects that could damage the PVC pipe.

I highly recommend using sand for backfilling (at least until the pipe inside the trench is hidden under its layer). In this case, the pipe is more reliably protected from soil shifts and, accordingly, depressurization.

In any case, backfilling should be done in layers, especially on the sides of the pipe, with intermediate compaction of the soil. This, again, is necessary to protect the engineering system from damage. You only need to compact the soil on the sides of the pipe, never on top. Plastic may not withstand such intense exposure.

A small mound should be poured on top, which is needed to compensate for the shrinkage of the soil after it gets wet.

By the way, if you plan to install wastewater treatment plants with some electrical equipment (for example, biological treatment stations), I advise you to immediately lay a shielded electrical cable in the ditch before backfilling. So that you don’t have to worry about connecting electrical devices to the network later.

Construction of a wastewater treatment plant

In addition to pipelines, part of the external sewerage system is a local treatment facility. As a last resort, I suggest using a septic tank made of concrete rings, which copes well with the tasks and is quite simple to do.

Carrying out calculations

At my son’s dacha, I decided to build a three-chamber filter septic tank. Of course, you can say that its power is excessive for a structure where people are not expected to live permanently. But I decided to make a foundation for the future.

Moreover, this option has many advantages:

construction and operation of a septic tank is cheaper than a biological treatment plant;
you can build it yourself, without involving outside specialists (looking ahead, I can say that I only needed an excavator to dig a pit and a crane to install concrete rings).

Among the disadvantages, I can only highlight the possible appearance of an unpleasant odor (solved by installing a ventilation pipe) and the need to remove sludge from the bottom.

So, my septic tank will consist of three different chambers:

for primary sedimentation of sewage waste;
for purifying liquids from biological contaminants;
to remove purified water through the filter bottom of the chamber.

Some people replace the last compartment with drainage fields, but I decided to limit myself to this design so as not to carry out a large amount of excavation work.

If you are not going to install at your dacha washing machine and invite a large number of people there to relax, you can limit yourself to one chamber, which will serve to remove solid inclusions.

Now about the size of the cameras. Let me give you some calculations. Let's say that 5 people are expected to live at the dacha (well, the calculation is to replenish the family). Each of them consumes about 200 liters of water within 24 hours, that is, the treatment plant must be able to receive 1000 liters of liquid per day.

According to regulatory documents and sanitary requirements, the local treatment plant must have such a volume as to accommodate triple the volume of dirty water, that is, about 3 thousand liters.

If the volume of a concrete ring is 0.6 cubic meters of water, then about 5 rings will be needed to build a septic tank. We divide it into three sections - it turns out that each chamber will have 2-3 rings. I'll do three to be sure.

Choosing an installation location

The second important point after calculating the required volume is the choice of location for installation. Moreover, this is done not at will, but in accordance with existing sanitary requirements.

The following requirements must be taken into account:

The minimum distance from a residential building to a septic tank should be 5 meters or more.
If you make a septic tank at a distance of more than 15 meters, you will have to pull a long pipe and make an inspection hole on it with a well for inspection. So I don’t recommend digging the pit too far.
The distance from the water intake source (well or well) to the treatment plant must be at least 30 meters.

By the way, one such moment. No matter how well and for a long time the septic tank works, sooner or later it will be necessary to clean it of bottom silt deposits using sewage disposal equipment. Therefore, you need to think about how this unit will approach your structure.

Excavation

The next stage is excavation work again. This is not a narrow ditch; you will have to remove a fairly large amount of soil, so I immediately advise you to either hire workers or order an excavator.

The size of the pit should be slightly larger than the diameter of the concrete rings used. That is, if we take rings with a diameter of 2 meters, the pit should have a width of 2.5 meters. Then this space will be filled with clay to prevent sewage from seeping into the ground when the well is depressurized.

The depth of the well depends on the number of concrete rings used. Fold the height of the parts and go deep into the ground so that after installation and arrangement of the concrete floor are completed, only the inspection hatch remains visible from above to check the operation of the septic tank.

Installation of rings

To install reinforced concrete parts you will definitely need a crane. Otherwise, construction will take away your last remaining health. Despite the fact that the operation of special equipment requires additional costs, you will receive a durable, strong and sealed treatment facility that is well worth the money spent.

The installation itself is as simple as possible. You just need to lay the parts one on top of the other, making sure that the walls are oriented strictly vertically. The joints must be reinforced with cement mortar. If the soil at the dacha is subject to shifting and swelling, metal brackets can be used to strengthen the treatment plant.

To prevent movement of concrete rings, the bottom of the trench should be prepared before installing them. You need to make a cushion of crushed stone there, compacting it thoroughly.

The biggest hassle will be with arranging the bottom. In the first two chambers it must be completely sealed to prevent waste from seeping into the soil, and in the third well a filter pad made of crushed stone will need to be left.

I’ll tell you more about arranging a sealed bottom:

The bottom of the first two wells should be thoroughly compacted again, after which a reinforcing frame made of metal mesh or reinforcing bars should be made below. I always drill a little into the walls at the bottom to insert pieces of reinforcement into the concrete rings and ensure a good connection between the floor and the walls.
After this, prepare a concrete solution from sand, crushed stone and cement, which is used to fill the lower part of the well, leveling the surface with a trowel.
Work on the construction of septic tanks can continue only after the concrete solution has completely hardened. This usually takes from 2 to 3 weeks depending on the air temperature.

Construction stores sell sections of concrete rings already equipped with a concrete bottom. You can buy yourself two of these parts and not waste time and effort on concreting the bottom of the treatment plant. But a pillow at the bottom is still needed so that the entire structure does not move during operation.

Sealing

To prevent sewage from seeping into the soil, the inner walls of the well should be carefully sealed. For this, I recommend using a special mixture, for example, Aquabarrier.

To be on the safe side, I decided to seal the surface with bitumen resin-based coating waterproofing. Some go even further by installing plastic liners inside concrete tanks to keep water out.

At the same time as sealing, overflow pipes must be installed. This is done according to the following scheme:

The first pipe that connects the septic tank to a residential building is installed in the first chamber of the septic tank at a distance of about 50 cm from its upper part. Although this is purely subjective, because it all depends on the depth at which your pipes are laid.
The second pipe (between the first and second chambers) should also be installed at the top, but slightly lower than the first. The point is to pour out the settled water that accumulates at the top of the chamber through it.
The second and third chambers are connected in a similar way.

On the picture - approximate diagram placement of pipes in the septic tank.

backfilling

The last stage of construction of the treatment plant and the entire external sewage system is backfilling the septic tank. You can use the soil that you took out when preparing the pit, but I additionally bought fatty clay and filled the space around the wells with it. Thus, I created an additional barrier to prevent sewage from seeping into the soil.

Conclusion

External sewerage is perhaps the more important component of the wastewater disposal system in summer cottage, how inner part this utility network. To clearly see the installation process, you can watch the video in this article. And if you have any questions or your own advice, you can leave them in the comments to the material.

July 18, 2016

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The smallest depth at which a street sewerage network can be laid can be determined by taking into account the possibility of connecting to its system the longest line of the intra-block network with a slope of 0.007. The smallest depth for laying the initial elements of the intra-block network is taken to be 30 cm less than the depth of soil freezing and not less than 50 cm from the surface.

If the sewer network is clogged, it is necessary to inspect, flush and clean it. To do this, inspection wells are installed wherever there are changes in the diameter and slope of the pipes, where there are turns, and on straight segments of a sewer line that has the same diameter. In places where rivers, ravines, railway tracks, etc. intersect with the network, overpasses or siphons are installed. Duckers are made from metal pipes, laid at the bottom of a ravine, river or under railway tracks. Dykers operate under the natural pressure of flowing wastewater. Overpasses have the form of a bridge covering an obstacle, along which a sewer pipe with a rear slope is laid in a protective box.

Flushing the sewer network from sediments constantly forming at the bottom of sewer pipes (in areas where the flow rate of wastewater is insufficient) is carried out by accumulating incoming wastewater in inspection wells (the lower hole of the well is closed with a portable shield) and quickly emptying them into the sewer network (when the shield is opened ). Thanks to these actions, a high speed of water movement is created, with the help of which all accumulated sediment is removed.

If a section of the network has an insufficient influx of wastewater, then the inspection well is filled with water through the fire hose of the hydrant available in water supply network. In some cases, special flushing wells with a capacity of up to 2 m³ are installed in the initial sections of the network. They are filled with water from the water supply and connected to the sewer line.

Creation of a small sewer network for individual developments

Tools and materials needed to create an individual sewer network: digging tools, pipes, crushed stone, sand, tees, oblique crosses, tow, measuring instruments and tools for plumbing work.

During the construction process, it is necessary to take into account a number of sanitary and hygienic requirements and provide the opportunity to remove wastewater from toilets, sinks, washbasins, showers, bathtubs, etc.

To receive wastewater in all rooms on the site, sewer pipes with a nominal diameter of at least 25 mm are used. All pipes and fittings for the device internal system sewers must comply with all technical specifications, satisfy sanitary standards.

External sewerage networks are located outside residential premises. The system is designed to drain wastewater and further purify it. Installation of an external sewer system is strictly regulated regulations- SNiPs.

Classification of external sewer networks

External sewer networks, depending on the method of their organization, are divided into several types:

systems where household wastewater and rain or melt water are transported separately and to different collectors are called separate;
networks where rainwater and household wastewater is transported separately, but enters a common collector and is called semi-separate;
systems without dividing water into domestic and rainwater are called all-floating.

The most effective, from an environmental point of view, is a separate sewer system. It is more expedient to install the same sewer system for domestic needs on a personal plot.

Main elements of external sewer networks

The external sewer network is complex design. As a rule, it includes:

metal or polyethylene pipelines of various diameters intended for the passage of liquid;

for various purposes: for viewing, for rotating the system, for arranging level differences. In most cases, reinforced concrete is used for devices, but durable plastics can also be used;

collectors, which are large-diameter pipes into which water flows from the storm sewer network or domestic systems;
specialized . Installed in places where it is impossible to equip the passage of liquid by gravity;

various local types intended for primary wastewater treatment;

discharges of water into external sewer networks or into bodies of water, for example, ponds.

Do-it-yourself installation of domestic external sewerage

Installing sewerage: external networks and structures is quite simple if you adhere to the basic rules:

trenches dug for should contain a slope sufficient for gravity flow of liquid. If you do not comply with these standards, you will need to additionally install pumping stations, which will complicate the work and negatively affect the cost of the system.
Before installing the pipeline, the necessary equipment is installed: local treatment systems, wells provided for by the project.
on a long straight section of the pipeline, the distance from one well to another should be at least 15 - 18 meters.
It is more convenient to start installing the pipeline from the last outlet pipe.
It is more expedient to connect pipes by welding into a socket.

If the above rules are observed, the sewer system will work flawlessly for a long time.

Sewerage project

Like many other types of construction work, installation of an external sewer network begins with a project. It is best to entrust such work to specialists, but you can develop it yourself.

At the first stage of design, it is necessary to establish where wastewater will flow in the future. It can be:

centralized external sewer network. To connect to this system, it is necessary to carry out work to collect the documentation established by law. This connection is considered the best;
special sealed wastewater storage tank. Such a system is periodically cleaned by machines, so it is advisable to install the tank closer to the fence and roadway for ease of access by equipment;
local treatment facilities for further use of water, for example, for watering a garden or for discharging treated water into the nearest body of water.

The next step is to study climatic conditions the area in which the external sewage system is supposed to be located:

find out the depth of freezing of the ground, on which the depth of the network depends. If it is not possible to lay pipes and structures below the freezing layer, then you will need to purchase special insulation for pipes, for example, glass wool.

examine the terrain. Is it possible to install a gravity sewer on the site or in mandatory the use of pumping stations will be required.
find out the type of soil and the level of groundwater. If the water is located close to the surface, then the possibility of laying pipes below the freezing depth is completely excluded. The type of soil affects the layer of protective cushion for the pipes, which is constructed from sand. If the site has heavy soils, then the protective layer should be larger.

At the last stage, some indicators necessary for the correct operation of the sewer network are calculated:

amount of wastewater. It is estimated that one person needs about 200 liters of water per day.
pipeline laying slope. According to SNiP requirements, for pipes with a diameter of no more than 200 mm, it is enough to make a slope of 2 cm for every 2 m of the pipeline.
the required volume of a septic tank for an autonomous sewage system. The average course of wastewater disinfection occurs within 3 days.

It is better to entrust the design of external sewerage to specialists. As a last resort, you can carry out design work yourself, strictly following the recommendations.

Sewage installation

Installing a sewer system is somewhat easier than designing it. You can do this work yourself. For this:

trenches are dug for pipelines and designated structures. The minimum margin in dimensions should be at least 20 cm, which is necessary for the convenience of laying the network.

A layer of sand is placed at the bottom of all trenches.
structures are installed: pumps, treatment facilities, wells, and so on.
mounted external network sewerage.

pipelines are laid in trenches and covered with a layer of sand.

The soil is laid using the backfill method.

An external sewer network is necessary on a personal plot. This system of structures will help preserve the environment. environment and without additional effort obtain water for watering garden plants.

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When installing such systems, a sewage disposal truck will not be needed.

It’s better to save up a sufficient amount, install a treatment plant and no longer worry about the environment, the smell, or the reliability of the waste water disposal system.

External pipeline supplying sewage to receiving devices

Having collected all the wastewater from the kitchen, bathroom, laundry room, shower, bathhouse, and toilet through the internal piping system of the building, they must be discharged through external sewer networks to reception facilities for treatment.

For this purpose, external drainage networks are installed.

External sewerage (wastewater) networks in private areas are mostly made of plastic pipes, calculated according to the diameter during the implementation of the project.

For laying external networks, use special, most durable pipe products intended for external work, including fittings for them. Such pipes are painted orange or yellow-brown. Other colors of pipes are intended for internal laying of the drainage network.

Polypropylene corrugated pipes are considered particularly durable.

The pipeline is installed with a slope to the receiving system of 2-3 degrees, starting installation from the lowest point, that is, from a cesspool, septic tank or deep wastewater treatment plant.

To maintain the sewerage network route, it is mandatory to install inspection wells at each branch of the sewerage network, and on straight sections of the pipeline, wells are made in increments of 10-12 m.

To ensure that sewer networks function properly, for a long time and there was no need to urgently alter them, requiring excavation of the soil; all work must be carried out carefully according to a well-developed project in accordance with building codes and regulations (SNiP).

Nomenclature of used pipes and auxiliary elements of the water supply and sewerage network

For large-diameter main networks, steel, cast iron, asbestos-cement, ceramic and reinforced concrete pipes are used.

For local pipelines - steel, cast iron, ceramic and plastic.

In modern construction, plastic systems for transporting water and wastewater are most widespread in terms of price and quality ratio.

Their advantages over other types are:

complete absence of such a parameter as corrosion;
good resistance to the aggressive environment of sewage waste;
pipe strength and ability to take on soil loads;
unhindered passage of drains due to the smooth inner surface of the installed pipes;
low weight of pipes and easy installation of the pipeline system;
a large assortment and variety of polymers used for the production of pipes.

Pipelines made of polyvinyl chloride (PVC)

Connections of such pipes are made using special tools.

Such connections are mounted “in a socket” or using a special “cold welding” adhesive.

PVC pipes are rigid, and if it is necessary to make turns, bends and other operations, special fittings are used - bends and tees.

They withstand the load well when planted in the ground.

In addition, they are quite affordable in price.

Pipeline using polypropylene pipes

Polypropylene pipes are available in single- and multi-layer types.

Single-layer pipes consist of a thick layer of polypropylene.

Multilayer pipe products consist of two layers of polypropylene, and between them there is a layer of aluminum foil.

Connections during installation are made using a fitting or by welding, using special welding machines for polymer pipelines.

High-pressure (LDPE) and low-pressure polyethylene pipes (LDPE)

These pipes have a very low operating temperature limit.

They are produced using two technologies using high and low pressure.

Polyethylene pipes are elastic and are transported in coils. Such pipes are good for making turns in the pipeline network.

They are connected to each other using fittings and welding operations.

Particularly durable and thermally resistant pipes made of cross-linked polyethylene.

Intersection of external and underground water supply and sewerage networks

In cases where it is necessary to intersect water supply and sewerage networks, such intersections are made at a right angle or close to it.

Steel water supply pipes are laid at the intersection with the sewerage system 0.4 m above the drainage network. When using cast iron pipes, it is necessary to use a steel casing. The length of the casing in either direction from the intersection is at least 5 m in clayey, heavy soils, and 10 meters in sandy and sandy loam soils.

Local sewer networks may be installed above networks providing water supply to buildings without casing, with a distance between the walls of the pipelines along the vertical axis of at least 0.5-0.7 m.

When laying water supply and sewerage networks in parallel at the same level, the distance between the walls of the laid pipes must be at least 1.5 m for a nominal diameter of a pipeline with a diameter of 200 mm inclusive, and at least 3 m for a nominal diameter of more than 200 mm.

When installing a water supply passing below drainage pipes, the above distances along the horizontal axis are increased by the difference in depth marks of the laid pipeline networks.

The main element of any sewerage (wastewater) system, except for export, is the external sewer network.

An external sewer network is a system of pipes laid in the ground and wells on them, designed to collect one or more types of wastewater and divert them to places of treatment or discharge.

The external sewer network includes the yard and street networks, as well as a collector (general drainage pipeline).

The yard network receives wastewater from one building or group buildings within the same yard and discharges it into the street network.

The street network receives wastewater from yard networks and discharges it into a common collector pipeline.

Through the collector, wastewater flows to treatment facilities or to the point of its release into a reservoir or onto the terrain.

Wells for various purposes are installed on the yard and street sewer networks, as well as on the collector, which ensure reliable operation of the external sewer network of the facility during its operation.

3.3.1. External sewer network diagrams

The design of the external sewer network must reflect the conditions for the removal of wastewater from all sewerage facilities, ensuring the minimum length of the network and the smallest depth of pipes.

Depending on the nature of the movement of wastewater through the pipes of the sewer network, it can have two schemes - gravity and pressure-gravity (gravity-pressure).

With a gravity sewer network, the movement of all types of wastewater from the entire territory of the sewer facility to the treatment plant or outlet occurs by gravity, due to the slope of the pipes.

In the pressure-gravity scheme of the sewer network, in some areas the movement of wastewater is carried out under the pressure created by pumping stations, in others - by gravity.

In each specific case, the flow pattern of wastewater in the external sewer network is determined based on the terrain and the requirement for the security of the sewer facility.

According to the design of the sewer street network and the collective in the plan, in relation to the drain (reservoir) into which treated wastewater is discharged, five schemes can be distinguished:

1. Perpendicular scheme, which involves laying the street network and collector perpendicular to the bank of the watercourse (reservoir) (Figure 13 a). This scheme is used when the terrain has a pronounced slope towards a watercourse (reservoir) for the removal of rain and unpolluted technical wastewater that does not require treatment.

2. Intersected scheme, in which the street network is laid perpendicularly, and the collector is laid parallel or at some angle to the bank of the watercourse (reservoir) (Figure 13 b). This scheme is used when it is necessary to treat all wastewater and there is a slight slope of the terrain towards the watercourse (reservoir). With a steep slope of the terrain, the use of a rugged scheme can lead to high speeds of wastewater movement in pipes, especially street networks, which is dangerous for their mechanical strength.

According to this scheme, a sewer network of a general sewerage system can be arranged, as well as for the disposal of domestic and contaminated technical wastewater of separate and incomplete separate sewerage systems.

Rice. 13. Schemes of the sewer network.

a-perpendicular; b-intersected; in-parallel; g-zone; d-radial.

The advantage of the crossed scheme is the possibility of draining wastewater by gravity with minimal deepening of pipes laid using the slope of the terrain.

3. A parallel scheme is in which the street sewer network is laid parallel to the shoreline of a watercourse (reservoir) or at a certain angle to it, and the collector is laid along the shore (Figure 13 c). The use of this scheme is advisable in the presence of large slopes of the terrain from the canalized object to the bank of the watercourse (reservoir). When using a parallel scheme in areas with small terrain slopes towards a reservoir (watercourse), a significant deepening of the collector or the construction of pumping stations on it will be required, which will increase the cost of the sewerage system as a whole. In these cases, it is necessary to lay the street sewer network and collector at an angle to the bank of the watercourse (reservoir).

4. The zone scheme consists of several independent street sewer networks and prefabricated collectors that discharge wastewater from a certain part (zone) of the sewerage facility (Figure 13 d). This scheme is used when, due to the site layout and terrain conditions, it is not possible to drain wastewater by gravity from the entire sewerage facility to the treatment plant. In this case, the sewerage area is divided into several zones. Wastewater one of the zones enters the treatment plants by gravity, and wastewater from the collectors of other zones is supplied by pumping stations (sewage pumping stations), which are located at the end of each collector, to the collector of this zone or directly to the treatment plants located radially.

5. The radial scheme includes several independent street sewer networks with collectors and treatment facilities (Figure 13e). This scheme is used on sites with buildings dispersed over a large area and poorly defined (flat) terrain, as well as for sewerage of large populated areas.

The external sewer network scheme in each specific case is selected based on a technical and economic assessment of options developed taking into account local conditions, facility layout and other factors.

In terms of economic indicators, the most effective are perpendicular, crossed and zone schemes. With a parallel scheme, there is a large length of the sewer network, and with a radial scheme, there is the construction of several treatment facilities.